public class _计算值 {
    public static void main(String[] args) {
        int i = 0;
        double count = 0;
        for(i = 1;i <=100; i++){
            if( i%2 == 0 ){
                count -= 1.0/i;
            }else{
                count += 1.0/i;
            }
        }
        System.out.println(count);
    }
}
